P-trap arm need slope? slow draining issue queston

[729zoom]

can someone tell me if the p-trap arm (the horizontal pipe that connects the ptrap to drain pipe in the wall) it supposed to have a slight slope towards the drain pipe in the wall? We are having slow drainage that we know is not due to a clog in the pipe or vent. Google Gemini (AI) says if the ptrap arm is level or sloped towards the ptrap that it will cause the same issue as not having an overflow. I have been given bad info by the AI bots so wanted to ask the humans, as I can't find much when I google and none of the videos we downloaded mention this. I took a level and it looks like the arm we installed where the sink drains so slow is level with maybe a tiny slope back towards the ptrap. So, if google AI is right, this would be why we are having this issue? I don't want to spend time this weekend redoing the pipes for no reason so hope a plumber with experience can tell me if on the right track.

 

[Reach4]

Trap arm should be sloped, but a flat (or slightly backsloped) trap arm is probably not the cause of your slow drainage.

Slip joint or glued trap?

Kitchen sink with a disposal? Maybe post a photo.

 

[Sponsor]

 

[729zoom]

Trap arm should be sloped, but a flat (or slightly backsloped) trap arm is probably not the cause of your slow drainage.

Slip joint or glued trap?

Kitchen sink with a disposal? Maybe post a photo.

Hi, it is slip joint and a bathroom sink. My husband insists that it is already sloped towards the wall so his level and mine do not concur so I will check again. Regardless, it sounds like it is something else and we can't figure it out. The bathtub and toilet in the bathroom drain fine. We snaked the drain and even the vent from the roof

 

[Weekend Handyman]

I am not a plumber. It is likely filled with biofilm. Just pop the trap off and look … 1/2 hour job, max.

 

[WorthFlorida]

The biggest problem with bathroom sinks is hair right at the drain stopper. . Remove the trip lever and pull out the stopper.

 

[Reach4]

Turn each level around 180, and the correct one will give the same indication with each orientation.

If you did want to add slope, just take the stuff apart. After you are sure the tubing is clear, shorten the tailpiece extension by about 1/4 inch. Put things back together, and you will have slope.

When I had a lav drain that was slow, the blockage was where the drain pipe transitioned from vertical to horizontal. But certainly pulling the stopper and looking/cleaning there is good.

https://terrylove.com/forums/index.php?threads/trouble-snaking-bathtub-drain.95143/ #3 describes my cure.
Also https://terrylove.com/forums/index.php?threads/help-bathroom-faucet-sink-is-badly-clogged.92361/ #12.

 

[Weekend Handyman]

The biggest problem with bathroom sinks is hair right at the drain stopper. . Remove the trip lever and pull out the stopper.

View attachment 100864View attachment 100865

I did not initially see that in the pic … you are likely right.

 

[729zoom]

I am not a plumber. It is likely filled with biofilm. Just pop the trap off and look … 1/2 hour job, max.

the sink is new and my husband just put that ptrap in. We just started using it a couple of days ago so no hair or soap or anything has passed through that. He snaked the drain before he did that and again after it was slow. And he went on the roof and snaked the vents as well. And the bathtub next to it drains great and I THINK shares the same drain downstream? but we are at a loss so I thought it might be the slope in the arm.

 

[729zoom]

I did not initially see that in the pic … you are likely right.

when you say I am likely right, are you referring to me thinking it might be the slope of the ptrap arm that goes to the wall? Or are you referring to another comment?

 

[729zoom]

The biggest problem with bathroom sinks is hair right at the drain stopper. . Remove the trip lever and pull out the stopper.

View attachment 100864View attachment 100865

no hair in the sink. It has not even been used yet. It was recently installed so all new trap, etc. and my husband snaked the drain twice. He has one that goes a long way.

 

[729zoom]

Turn each level around 180, and the correct one will give the same indication with each orientation.

If you did want to add slope, just take the stuff apart. After you are sure the tubing is clear, shorten the tailpiece extension by about 1/4 inch. Put things back together, and you will have slope.

When I had a lav drain that was slow, the blockage was where the drain pipe transitioned from vertical to horizontal. But certainly pulling the stopper and looking/cleaning there is good.

https://terrylove.com/forums/index.php?threads/trouble-snaking-bathtub-drain.95143/ #3 describes my cure.
Also https://terrylove.com/forums/index.php?threads/help-bathroom-faucet-sink-is-badly-clogged.92361/ #12.

so, since we know there is no hair or anything clogging the pipe anywhere (as newly installed and sink virtually unused) do you think possible that the slope of the arm is off or could it be something else like that? It drains like a sink that has no overflow. But it does have overflow.

 

[Reach4]

so, since we know there is no hair or anything clogging the pipe anywhere (as newly installed and sink virtually unused) do you think possible that the slope of the arm is off or could it be something else like that? It drains like a sink that has no overflow. But it does have overflow.

Good observation about a sink with no overflow. If the drain is one not made to receive an overflow or the opening to the overflow is not lined up, that can let pressure under the stopper slow the flow.

Remove the stopper temporarily. Does the sink drain readily then?

If no, after things sit for a while, see how much water you can quickly add, before the draining gets slow. From that, we can estimate how far the pipes are until the partial clog.

Another test is to fill the bowl to the overflow. Then open the drain. Does that drain more quickly?

 

[729zoom]

Good observation about a sink with no overflow. If the drain is one not made to receive an overflow or the opening to the overflow is not lined up, that can let pressure under the stopper slow the flow.

Remove the stopper temporarily. Does the sink drain readily then?

If no, after things sit for a while, see how much water you can quickly add, before the draining gets slow. From that, we can estimate how far the pipes are until the partial clog.

Another test is to fill the bowl to the overflow. Then open the drain. Does that drain more quickly?

the sink has an overflow. It just drains the same as if it did not. Like a sink without overflow, it drains well at first and then starts to slow. If I turn the water on all the way, it drains well for 15-20 seconds and then begins to fill up.

I just filled it all the way to the overflow and then released the drain stopper and a big air bubble came up and then it drains very, very slow - even slower. I took a video and couldn't attach so uploaded to youtube here:

https://youtu.be/8GZOCPsceSo

 

[GReynolds929]

From what I see in the video there's an obstruction downstream.

 

[729zoom]

From what I see in the video there's an obstruction downstream.

I wonder why the tub, sharing the same drain is ok and this happening even though the drain was snaked and the pipes were just put in. It's sooooo weird. The clog is now worse and just now, when I tried a plunger, every time I plunged, water spit out of the overflow.

 

[Reach4]

I wonder why the tub, sharing the same drain is ok and this happening even though the drain was snaked and the pipes were just put in. It's sooooo weird. The clog is now worse and just now, when I tried a plunger, every time I plunged, water spit out of the overflow.

Informative... water squirting out of the overflow does show that the overflow is functional.

A snake can take the wrong path.

In snaking with a small snake head, the snake can push through, and then when the snake is withdrawn, the fat or hair blob can partially close back up.

How did your husband snake from the sink?

Edit to add:
See https://www.engineeringtoolbox.com/pipe-water-content-volume-weight-d_1734.html (gallons/ft) column. If I assume the average pipe diameter to your clog is 1.5 inches, and if I presume you add 1 gallon of water quickly before the backup occurs, I could come up with 1/ 0.091=11 ft.

That is rough estimate. The diameter in the trap and trap arm is less. Plus the vent pipe will fill up to the level of water in the sink. Plus some of the path could be 2-inch pipe. Plus some water will make it thru the small clog while the water level rises. But still, this can be a useful thing.

 

[Weekend Handyman]

when you say I am likely right, are you referring to me thinking it might be the slope of the ptrap arm that goes to the wall? Or are you referring to another comment?

Sorry … I was unclear. I was referring to Post#5.